Pathlight 2022 Prelim 4E Computing P1 ANSWERS

4E Computing Paper 1 PRELIM 2022 1 2022 PRELIMINARY EXAMINATION Secondary 4 Express Computing Paper 1 ANSWERS AND MARKING SCHEME 1 (a) data corruption Data corruption occurs when computer data is made unusable by errors or alterations. [1] (b) any three: • Human error • Power failure • Hardware failure or damage • Malicious software [3] (c) perform regular backups [1] 2 (a) A316 = 1010 00112 = 1 x 27 + 1 x 25 + 1 x 21 +1 x 20 [1] = 128 + 32 + 2 + 1 = 16310 [1] (b) 10110112 = 1 x 26 + 1 x 24 + 1 x 23 + 1 x 21 +1 x 20 [1] = (64 + 16 + 8 + 2 + 1)10 = 9110 [1] (c) 10510 = 26 + 25 + 23 + 20 [1] = 0110 10012 (must be 8 bits) [1] 0 1 0 1 1 0 1 1 0 1 1 0 1 0 0 1

4E Computing Paper 1 PRELIM 2022 2 3 (a) Cell Data type A1 Text A2 Date B3 Currency F1 Percentage [4] (b) G8 =SUM(B2:B6) [2] (c) SUMIF(C2:C6,”Yes”,B2:B6) [1] The function is entered with 3 arguments, first the range where the criteria is contained is selected, then the criteria is entered, in this case “Yes”, then the sum range of cell is selected. The function then returns the sum of the corresponding cells that meet the criteria, in this case, cells B3:B4. [2]

4E Computing Paper 1 PRELIM 2022 3 4 Security Threat Description [6] Cookie A computer program that pretends to be a harmless file or useful application Pharming Phishing Spamming A small file used by websites to store personal information on a user’s web browser A computer program that attaches itself to a normally harmless program and modifies it The use of emails and fake websites that appear to be from reputable companies in order to steal personal information such as passwords and credit card numbers from users The use of data owned by someone by someone else, such as an intruder, without permission Trojan Horse The mass distribution of unwanted messages or advertising to email addresses collected from sources such as public mailing lists, social networking sites, company websites and blogs Virus The interception of requests sent from a computer to a legitimate website and redirection to a fake website to steal personal data or credit card details

4E Computing Paper 1 PRELIM 2022 4 5 (a) 5 marks for correct logic gates used, 1 mark for correct output. [6] 5 (b) 4 marks for correct output for X (1 mark for each pair of correct output). [4] A B C Working Space R S T U V X 0 0 0 0 1 1 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 1 1 0 1 1 0 1 1 0 0 0 0 0 0 1 0 0 0 1 1 0 0 0 1 0 1 0 1 0 0 0 0 1 1 0 1 1 1 1 1 1 1 1 1 1 1 0 1 0 1

4E Computing Paper 1 PRELIM 2022 5 6 (a) router and switch (i)Similarity: Both router and switch are both network connecting devices used to connect devices in a LAN [1] Difference: While a switch combines multiple similar networks that use the same protocol into a single network, a router keeps the connected ne tworks (which may use fundamentally different protocols) separate and forwards packets between them using Internet protocols. [1] (ii) Another device (1 mark for naming, 1 mark for describing the function): Network interface card: A network interface controller (NIC) provides the hardware interface to enable the transfer of data between a device and a network. Network Hub: Used to connect multiple devices to the same network; it transmits received packets to all connected devices Modem: When setting up Internet access in a home network, an ISP will typically provide a modem that sets up a long-distance connection to the ISP’s network. [2] (b) Ashley’s home network is a LAN. It is within a building (his home and covers a small geographical area. [3] 7 (a) (i) Trace Table: Count Number1 Number2 OUTPUT 0 7 2 Win 1 4 4 Draw 2 6 8 Lose 3 [4] (b) (i) Range check - to check that user has entered numbers greater than zero [2] (ii) Format check Presence check [2] (c) Test case condition Test data Boundary condition 0, 10 Error condition Any reasonable test data: -1, twelve, three 1 mark each for test case condition identified, 1 mark each for test data [4]

4E Computing Paper 1 PRELIM 2022 6 8 Creative works that have value but can exist purely as data with no physical form are known as …………intellectual………… ………property………… .[1m] Owners of such works can grant a ………licence……… [1m]……………… to authorise for use under certain conditions. Software where the legal protections have either expired or are inapplicable are known as ………public………………… …………domain………… software.[1m] ……Plagiarism…[1m]…………… is when a person passes off someone else’s original work as one’s own. [4] 9(a) There are 3 faulty conditions: - low fuel, low voltage and the brake pads are too thin. [2] (b) Write the correct parity bit in each of the following registers (even parity). 0 1 1 1 0 0 1 0 1 0 1 0 1 0 1 0 [2] (c) 8D [1] 10 One mark for each error identified and one mark for matching correction Line Error Correction 01 WithinRange = 999 WithinRange = 0 06 IF number >= 20 OR number <= 50 THEN IF number >= 20 AND number <= 50 THEN 10 Count = Count + 1 Not needed here 11 NEXT Y NEXT Count [8]

4E Computing Paper 1 PRELIM 2022 7 11 (a) input – item(type of item), quantity of item (1mark) output – total earnings, item with the highest earning (1mark) process – check input item, add cost to counter, repeat checking input item and adding cost to counter till “end” is entered, compare cost to find highest earning(max 2 marks) [3] (b) Marking points (any six): – 1 mark for complete initialisation – 1 mark for correct loop structure (could be while – end while or do – until loop.) – 1 mark for correct input of item INSIDE the loop – 1 mark to check on which item has been input – 1 mark for correct *summation of value of each item input – 1 mark to check if each item total is the largest value – 1 mark for variable (e.g. x) takes on the highest total value – 1 mark for total value of ALL four totals – 1 mark for correct output OUTSIDE the loop Sample coding: x,tbun, tcoffee, tcake, tsand =0,0,0,0,0 item = “” highest = “” WHILE item != “end” INPUT item INPUT quantity IF item = “bun” THEN tbun = tbun + 0.5* quantity ELSEIF item = “coffee” THEN tcoffee = tcoffee + 1.20* quantity ELSEIF item = “cake” THEN tcake = tcake + 1.50* quantity ELSEIF item = “sandwich” THEN tsand = tsand + 2.10* quantity ELSE OUTPUT “error” ENDIF ENDWHILE IF tbun > x THEN x = tbun, highest=”bun” IF tcoffee > x THEN x = tcoffee, highest =”coffee” IF tcake > x THEN x = tcake, highest =”cake” IF tsand > x THEN x = tsand, highest = “sandwich” total = tbun + tcoffee + tcake + tsand OUTPUT “Total Earnings is “, total OUTPUT “Highest Earning item is “, highest [6]